The extensive damaging effects of methamphetamine (METH) on brain function are well-documented. Unfortunately, at present, there are no effective treatments to prevent or reverse the neuronal damage inflicted by METH abuse. New findings implicate mitochondria-mediated apoptotic pathways in METH-induced neuronal death. Mitochondria, which are structurally organized into a highly regulated network, provide ATP for energy-demanding neuronal functions and also play a key role in the apoptotic cascade. In general, release of cytochrome c and other apoptogenic factors from mitochondria is accompanied by structural and functional mitochondrial defects, but the mechanisms of METH-induced mitochondrial injury are not understood. The goal of this project is, therefore, to explore a novel concept that fragmentation of the mitochondrial network associated with mitochondrial ultrastructural changes and bioenergetic dysfunction represents a critical pathway in METH-induced neurotoxicity. The project has two specific aims: (1) To test the hypothesis that METH induces mitochondrial fragmentation that results in cristae degradation and cytochrome c release. (2) To test the hypothesis that METH causes mitochondrial bioenergetic deficiency, in part mediated by mitochondrial fragmentation. This project will utilize several in vitro approaches deconvolution fluorescence microscopy and electron microscopy tomography to analyze mitochondrial structure will be combined with quantitative measurements of mitochondrial bioenergetic parameters such as respiration, mitochondrial membrane potential, cytochrome c, and ATP levels. Primary cortical neurons as well as dopaminergic neuronal cell lines will be used in this project.PROJECT NARRATIVE This project will help to understand the precise mechanisms by which METH damages mitochondria, the power plants of the cell. Gained knowledge will be essential for developing new therapeutic approaches aimed at restoration of normal energy levels in METH-affected brain cells and prevention of their loss.